Work-presenting mechanisms for blindstitch sewing machines



5 Sheets-Sheet l May 5, 1958 F. PARRY WORK-PRESENTING MECHANIsn/rs- FOR BLINDSTITCH SEWING MACHINES Filed Aug. 2, 1955 5 Sheets-Sheet 2 /NVE/VTOR Fran/r Parry y /r-Lk, y ATTORNEY w .m @E

F. -PARRY May 6, 1958 WORK-PRESENTING MECHANISMS FOR BLINDSTITCH SEWING MACHINES Filed Aug. 2, 1955 May 6, 1958 F. PARRY 2,833,234

WORK-PRESENTING MECHANISMS FOR BLINDSTITCH SEWING MACHINES Filed Aug. 2, 1955 3 Sheets-Sheet 3 //v VENTO/ F rank Parry W/TNESS @Y M Wy 14% United States Paten-t -WORKQPRESENTING MECHANISMS FOR -BLIND- STITCH SEWING MACHINES 'Frank zParry, Trumbull, Conn., assgnor to :The -Singer :Manufacturing CompanyyElizabetm-N. J., a corpora- :tion of New, Jersey Application August 2,1955, Serial No,y '525,970

SClaims. :(Cl. 112.178)

, lmatically operable control mechanism for the ridge former of :afblindstitch vsewing machine, ofthe iabove character whereby one or more skip stitches may ibezcaused tobe formed between successive anchorstitches.

Another object of this invention isto provide azskip iistitch mechanism for the ridge former .of' a Ablindstitch :sewing machine, operationof :whichtwillrzbesubstantially unaffected Vby adjustmentsin the 'height of the work- :supporting plate ofthe sewing machine.

Still another object of this invention `is tofprovide a throw-,out device for the vautomatic Iidge;former;control ymechanism which is Aconveniently accessible to the machine ,operation and whereby only anchorstitches may ybe ,caused to be formed.

"With-the above and additional objects Vandfadvantages in'view as `will hereinafter appear, this iinventionfcomprises the devices, combinations, and-.arrangementszof parts hereinafter described and illustratedin `the accompanying fidrawings of 1a preferred embodiment inwhich:

Fig. l represents a vertical sectional View of a blindystitch sewingmachine taken longitudinally of the ibase and through the standard -a-nd work table with portions of the work table height adjusting mechanism v,being broken away Vbetter to expose the lridge forming mecha- Fig. 2 represents a `horizontal,sectional view-,taken subvstantially along line 22, ,Fig. 1, `of the work table and showing the mechanism carried thereby in elevation.

`1`gig..3 represents a vertical sectional view; of the -work table taken substantially along line 3--3 ofFig. u1.

Fig. 4 is'an enlarged elevational'view .of thestandard extremity of the .work table showing the throw-out lever for the automatic ridge former controlling mechanism.

Fig.- 5 is a diagrammatic perspective view of the throwout connections for the automatic ridge -former vcontrolling mechanism showing in fulllines the positions ofthe parts when the automatic ridgefformer controlling mechanism is thrown into operation, and-in 'dashed vlines -needle in -the formation yof vchained stitches.

2,833,234 'Patented May 6,

yrice .2 sewing vhead and disposed Ato-operate-above'the throat- ,plate is a vlooper 14 which cooperates withy the.curved A -workfeeding member`15 supported in 4the-sewing head yis formed vwith depending work-engaging teeth 16 operative through slots. in'thevthroat-plate to engageand-advance the-work fabrics. The sewing head portion 12 of the machine frame projects forwardly from a bracket varm 17-supported by .a standard 181rising`froma machine base 1,9. Pivotally supportedriby means of astud-shaft 20 journaled in-bearning lugs v21-21'extending from `the machine `base is a Vwork supporting table.22 which extends laterally beneath the .throat-plate 13 at .ther/free extremity of the '-sewing head.

vOne or more workzpresser members. 25 carried :bythe ywork table and disposed in opposition .to thework-feeding member 15 are biased upwardlyby spring means (not zshown) acting between the wpresser members and the work table. vSuch `work presser'mechanisms `are quite Swell known in the art and reference may be had to the U. AS. Dearborn Patent No.v 1,592,446, Juiy 13, 1926 for amore complete disclosure of a work presser mechanismof ,this type.

Also carried by the work supporting table 22 is the ridge forming mechanism with which this invention is concerned. The ridge forming mechanism has for its ypurpose `to form a bight or ridge in thework suchthat the ridge projects upwardly through an opening in the throatplate 13 and into the path of the needle.

Referring to Figs. 2 and 3, the ridge forming vmechanism comprises .a blade-like fabric-'engaging `ridge forming element 2.6

Yfaston ya rockishaft 27'journa1ed on pintle pins 28-28 vformeractuating eccentric 33 on a main `driveshaft 34 Y journaled in the bracket arm and standard. The main `drive shaft 34, by connections well known to those vskilled in the-art, serves to actuate the needle 11 and the looper 14 in the formation of stitches as well as rto actuate the work feeding member to advance the work fabrics. The ridge forming element is, therefore, oscillated in `timed relation with the operation of the other work manipulating vdevices of the sewing machine so as to engage and position a ridge of fabric forpenetration by the needle on each forward stroke thereof and to release the work fabrics upon withdrawal of the needle so that the fabrics rmay be fed smoothly and easily before thesucceeding needler penetration.

In normal blindstitching operations with a sewing ,machine as described above, thatI ply of fabric whichwill ultimately become the outer or face ply of the linished stitched article is placed lowermost and against .the work table during blindstitching. The ridge forming element then dictates the degree of penetration ofthe fabrics by the needle. It is usually desirable `that ,the anchor stitches, i. e., those which join all of the plies being stitched, merely graze the face ply of fabric penetrating onlya portion of the fibers thereof so as to bury the sewing threads beneath the surface ofthe cloth, thus providing a seam invisible from theface of the finished article. In the machine illustrated inthe drawings, the extent of ridge formation, and consequently, the depth of needle penetration of the anchor stitches is accomplished by bodily adjustment of the work table about-the axis of the stud shaft 20 by which the table is journaled yon the machine frame. The'work table height adjusting mechanism illustrated in the accompanying drawings is more fully disclosed in my copending patent application Serial No. 463,089, led October 19, 1954, to which reference may be had for a complete description thereof. The work table height adjusting mechanism includes a bell crank lever 36 freely journaled on the stud shaft provided with a short depending arm 37 defining a stop against which bears a lug 38 formed on the work table. The bell crank is also formed with an elongated arm 39 extending through the machine base and the standard into engagement with a roller 40 `carried `by a vertical rod 41 slidable axially in a lug 42 formed in a wall of the standard 18. The rod 41 is provided with a threaded upper extremity 43 engaged by a threaded sleeve 44 journaled in the standard and locked against` axial movement by means of a pin 4S carried by the machine `frame and disposed in an annular slot 46 formed in the` sleeve. A knurled adjusting knob 47 is fixed on the sleeve 44 for adjusting the position of the bell crank lever 36, thus providing an adjustable positive stop detiining the upper `limit of movement of the work table beneath the throat-plate 13. A heavy spring 48 engages a pin 49 in the work table and is anchored by an adjustable plunger 50 fixed in the rear wall of the machine base to bias the work table against the depending stop arm 37 of the bell crank lever 36. The spring 48 thus can yield to permit downward movement of the work table beneath the throat plate under anabnormal condition as for instance to permit an abnormal thickness of fabric such as a cross-seam to pass between the work table and the throat-plate or to permit lthe worktable to be lowered for the introduction of the work. However, with this type of blindstitch sewing machine, the work table remains substantially stationary during normal stitching operations, oscillation of the ridge former therein serving to present the fabricsto the needle,

It is desirable in certain blindstitch sewing operations to produce a seam in which every stitch is not anl anchor stitch. In these seams one or more skip stitches must be made between successive anchor stitches. In the art of blindstitch sewing, the term skip stitch does not connote an imperfect stitch marked by the absence of thread concatenation as it does in other branches of the machine stitching art, but instead skip stitch refers to a perfectly formed stitch which is formed so as to penetrate less than the total number of layers of fabric being joined, i. e., a stitch which skips certain of the fabric plies.

In the sewing machine illustrated in the drawings, the character of any particular stitch, Whether an anchorstitch or a skip stitch, is determined by the elevation attained by the ridge former. When the elevation of the ridge former is lowered, the needle is caused to make a shallow penetration of the Work fabrics and a skip' stitch results.

Automatically operable Amechanism is provided for raising and lowering the elevation of the ridge former on alternate stitches so as to'cause the formation of a seam in which alternateV anchor and skip stitches are formed. To this end, a countershaft 52 is journaled in the machine standard beneath the main drive shaft 34. By means of a clip belt 53 and pulleys 54, S5 the countershaft is driven at one-half the speed of the main drive shaft. An eccentric 56 fast on the countershaft 52 is embraced by a pitman 57 which extends through the machine base and is connected by means of a pivot pin 58 to a substantially vertical link 59 pivoted by a pin 60 to the ridge former rock frame 29 on an axis spaced forwardly of the axis of the rock'frame pintle pins 30-30. The pivot pin 58 in the pitman is also embraced by one extremity of an anchor link 61rpivoted at its other extremity by means of a pin `62 to the upstanding end of a lever arm 63 fastupon a throw-out shaft'64 iournaled in the work supporting table 22. The throw-out shaft 64 extends outside the work supporting arm and through a plate 65 which maybe secured to the work table in any one of a range af angular positions about the throw-out shaft by means of fastening screws 66-66 which pass through slots 67--67 in the plate and are threaded into the work table. A hand lever 68 fast on the throw-out shaft is provided with a retractable plunger 69 biased by means of a leaf spring 70 toward the plate 65 and adapted to enter one of a pair of apertures 71-72 formed in the plate to lock the throw-out shaft in. either of two positions, i. e., in the position illustrated in Figs. l through 4 and in full lines Vin Fig. 5 in which the automatically operable skip stitch mechanism will be called into operation, or into the position illustrated in dashed lines in Fig. 5 in which the skip stitch mechanism will be thrown out of operation.

Referring to the diagrammatic view of Fig. 5, the hand lever 68, the throw-out shaft 64 and the lever arm 63 are fixed for movement as a unit and, in effect, constitute a crank of which the anchor link pivot pin 62 constitutes the crank pin. The pin 62, therefore, may be secured in selected position, i. e., in either the full line or the dashed line position illustrated in Fig. 5 depending upon which of the apertures 71 or 72 the plunger 69 is locked within. The pivot pin 58 carried in the pitman 57 can partake of movement Vonly along an arc having its center on the axis of the anchor link pivot pin 62. When the plunger 69 is positioned in the throw-out position within the plate aperture 72, the anchor link pivot pin will be axially aligned with'the pin 60 by which the connecting link 59 with the pitman 57 is connected with the rock frame. In this position, the pitman will partake of idle movements and since its motion will be a turning movement about the axis of the pin 60 no motion will be transmitted to the rock frame 29. In this position of 'the parts, the ridge former will cause full needle penetration and hence anchor stitch formation at each stitch.

When the plunger 69 is locked in the plate aperture 71 and the parts disposed in the full line position as shown in Figs. 1 through 5, the axis of the anchor link pivot pin 62 is shifted out of coincidence with that of the pivot pin 60. With this arrangement of parts, movement of the pitman 57 will result in oscillatory motion of the pivot pin 60 and hence of the rock frame 29. Since the skip stitch eccentric 56 is driven at one-half the speed of the main drive shaft 34, the rock frame will be depressed by the pitman 57 about the rock frame pintles 30--30 on every other stitch.` Since the ridge former shaft is offset from the axis of the rock frame pintles, alternate stitches, therefore, will be shallow thus providing a skip stitch between each anchor stitch.

Referring to Fig. 4, the enlarged slots 67-67 through which the fastening screws for the plate 65 pass provide for an angular adjustment of the plate by which the position of parts in the throw-out position may be adjusted to bring the pivot pins 62 and 60 into perfect alignment. By this construction all movement of the rocking frame 29 may be cancelled in the throw-out position of the parts.

While in the preferred embodiment of the drawings, a two-to-one ratio is obtained between the speed of the main drive shaft and of the skip stitch eccentric 56,*it

' will be apparent that other ratios may be obtained by selection of the desired speed ratio between themain drive shaft and the countershaft 52. Thus a three-to-one ratio, if provided, would cause operation of the skip stitch mechanism to result in the formation of two skip stitches between alternate anchor stitches.`

The above described skip-stitch mechanism is particularly advantageous in that adjustments of the height of the work table 22 by way of the knurled adjusting knob 47 and the bell crank 36 will have no appreciable effect upon the action of the skip stitch mechanism. With reference to Fig. 1, the line A-A has been drawn joining the axis of the skip stitch eccentric 56 and the axis of the work table pivot pin 20. The line A-A passes substantially through the axis of the pivotal connection 58 by which the skip stitch pitman 57 is operatively connected with the rock frame 29. Adjustment of the work table 22, therefore, about the pivot pin 20 will shift the pivot pin 58 `along an arc of which the line B in Fig. 1 is a tangent. The line B is also a tangent to an arc having its center on the axis of the eccentric 56, which arc would represent an idle movement of a point on the pitman 57 about the axis of the eccentric, a movement during which the ridge former would not be turned with respect to the rock frame 29.

Since during operation of the sewing machine both the axis of the eccentric 56 and that of the pin 58 move, the axes of the pins 20 and 58 and of the eccentric 56 will shift constantly into and out of perfect alignment. These shifts out of alignment will, however, be so small as to be negligible and, therefore, as a result of the substantial alignment of these points as stated above, adjustments of the height of the work supporting table will have no noticeable effect upon the operation of the skip stitch mechanism of the ridge former.

Having thus set forth the nature of the invention, what I claim herein is:

1. In a blindstitch sewing machine having a machine frame, -a work supporting table pivoted on said machine frame, manually operable means carried by said machine frame for turning said work supporting table with respect to said frame, a rock frame journaled in said work table and a ridge former journaled for oscillation in said rock frame, and skip stitch mechanism for said ridge former comprising, an eccentric carried by said machine frame, a pitman embracing said eccentric, a link pivoted on said rock frame on an axis parallel to that about which saidrock frame is journaled in.

said work table, a pivotal connection between said link and said pitman, and an anchor link pivoted on said machine frame and on said last mentioned pivotal connection, said last mentioned pivotal connection being disposed substantially on a line joining the pivotal axis of said work-supporting table and the pivotal axis of said eccentric to minimize the elect upon the skip stitch mechanism of angular adjustment of said work supporting table.

2. In a blindstitch sewing machine having a machine frame, a work supporting table pivoted on said machine frame, a rock frame journaled in said work table and =a ridge former journaled for oscillation in said rock frame, skip stitch mechanism for said ridge former comprising, an eccentric carried by said machine frame, a pitman embracing said eccentric, a connecting link, means pivoting said connecting link to said rock frame, a pivotal lconnection between said connecting link and said pitman, an anchor link embracing at one extremity the pivotal connection between said connecting link and said pitman, and -anchor link securing means carried by said work-supporting table effective to lock the other extremity of said anchor link to said work-supporting table in any selected one of a plurality of positions, one of said positions being in axial alignment with said means pivoting said connecting link to said rock frame.

3. In a blindstitch sewing machine having a machine frame, a work supporting table pivoted on said machine frame, a rock frame journaled in said work table and a ridge former journaled for oscillation in said rock frame, a skip stitch mechanism for said ridge former comprising, an eccentric carried by said machine frame, a pitman embracing said eccentric, a connecting link, means pivoting said connecting link to said rock frame, a pivotal connection between said connecting link and said pitman, an anchor link embracing at one extremity the pivotal connection between said connecting link and said pitman, and anchor link securing means comprising a crank journaled in said work-supporting table, a crank pin carried. by said crank and arranged in operative engagement with the other extremity of said anchor link, and operator inuenced means carried by. said crank for locking said crank pin in any one `of a plurality of positions, one of said positions being in axial alignment with said means pivoting said connecting link to said rock frame.

Mueller Mar. 4, 1947 Parry May 18, 1954 

